Patent GB-300743-A (GB)
Title: Improved circuit arrangements in automatic and semiautomatic telephone systems
IPC: H04Q1/32
Filed: 1927-09-21
Abstract: 300,743. Siemens Bros. & Co., Ltd., and Caswell, A. E. Sept. 21, 1927. Automatic and semi-automatic exchange systems. - In apparatus arranged to operate on receipt of trains of impulses, a dialling relay is energized before the reception of each of a number of trains of impulses and de-energizes at the end of the train, this operation being performed for at least one of said trains without the use of mechanical contacts. The invention is described in relation to a connector, and to a trunk-offering or test-clerk's distributor which entirely controls a special connector having no relays. Specification 122,235 is referred to. Connector. When the line and release relays A, B have energized, dialling relay C energizes over its winding 1, e2, e1 b2, short-circuiting winding 1 of auxiliary dialling relay E. The first train of impulses energizes C, E over windings 2, the initial circuit of C(1) and the shortcircuit round E(1) being broken and a circuit for E(1) being made over c1 At the end of the train C, E release in turn, steering relay ST energizing over c2, e3, and locking up. Relay C reenergizes over the initial circuit and the next impulse train operates C, E as before. Distributor. When the line and release relays A, B energize, relay C energizes over winding 1; n3 and e2, e1 in parallel; b3, followed by energization of E(1) over c2, b3. Relay A is energized from earth at n2 and is held over b1. Relay C is now held over u3 alone, so that at the end of the first impulse train over C(2), E(2), and magnet V, n3 has opened, and C, E release in turn, followed by re-energization of C. E(1), however, is shorted over c2, el, n1. Steering relay EA now operates so that the next impulse train operates magnet R, after which EA releases. Special connector busy. Battery is connected to wiper Z as below and busy relay G operates and locks up and busy tone is connected up at g2. Special connector free. Relay H operates over winding 1 when C re-energizes to switch the impulse circuit over h2 and wiper X to the vertical magnet of the special connector. Relay H locks up and connects guarding battery over h4 to wiper Z. After the next impulse train, relays EB, EA energize in turn and the last impulse train operates the rotary magnet of the connector. Relay RC then operates and locks up to close the speaking circuit, releasing EA. Completion of connection. If the wanted subscriber is engaged at the called end of a local call, he asks the calling subscriber to hang up, after which his own pre-selector seizes a first selector from which he obtains speaking current. If he is at the calling end he continues to receive current from the selector used in the local call. Release. When the operator removes his plug, relays A, B release, and A cannot again be energized to seize the distributor until n2, is restored. Relays C, H, EB, RC are disconnected, but since H is slow release, it is again operated over n2, b2, rc5, h5, H(2), wiper Z in series with offnormal contact and release magnet of the connector until the latter is at normal. The distributor ncw returns to normal.